Folding ladder

Abstract

A folding ladder comprising multiple ladder sections pivotally joined together to permit the ladder to be articulated into and locked in a variety of configurations. Each ladder section includes a pair of side rails and a plurality of spaced rungs. The ladder end sections are identical and interchangeable. The ladder middle sections are identical and interchangeable. All side rails are reinforced by steel rods. The ladder sections are hinged together at their ends along one side of the ladder by master-type pivots and are hinged together at their ends along the opposite side of the ladder by slave-type pivots. Master pivots may be adjusted to a first position allowing the ladder sections to be moved with a denting action and to a second position locking the ladder sections together in a selected position. Slave pivots follow the action of the master pivots, allowing all ladder adjustments to be made from one side. Side rails and rungs of each ladder section are formed integrally from resin impregnated glass fibers in a single molding operation. Only two different mold forms are required. An adjustable leveler is provided for legs of the end ladder section.

The invention claimed is: 
     
       1. A hinge joint for coupling together two adjoining sections of a folding ladder, said ladder sections each including a pair of parallel side rails, comprising: a first disk-like hinge component secured along the outer edge thereof to the end of one of said side rails of a first one of said ladder sections;   a second disk like hinge component secured along the outer edge thereof to the end of one of said side rails of a second one of said ladder sections;   said first hinge component being formed with a first central hub having an internally threaded bore extending axially therethrough;   said first hinge component having at least one stud-like protrusion extending above the surface of one face of said disk thereof from a point thereon spaced radially from the center of said hub thereof;   said second hinge component being formed with a second central hub having a bore extending axially therethrough;   said second hinge component having at least one depression formed on one face thereof at a point thereon spaced radially from the center of said hub thereof by a distance corresponding to said radial spacing of said protrusion of said first hinge component;   a spindle threaded along one end thereof; and   a shouldered bushing fixed to the end of said spindle opposite said threaded spindle end,   said spindle being threaded into said first hub of said first hinge component and extending through said bore of said second hub of said second hinge component,   said bushing being fixed to said end of said spindle so as to extend into said bore of said second hub from the one end of said second hub opposite said one face of said second hinge component with said shoulder of said bushing bearing on said one end of said second hub,   said first and second hinge components thereby being pivotally joined together with said one face of said first hinge component facing said one face of said second hinge component.   
     
     
       2. A hinge joint as claimed in claim 1, wherein: the diameter of said bore of said second hub is reduced near the end of said second hub opposite said one end thereof to form an internal shoulder within said bore of said second hub;   and with additionally:   a compression spring fitted over said end of said spindle opposite said threaded end thereof,   one end of said spring bearing on said internal shoulder of said second hub,   the opposite end of said spring bearing on said bushing, thereby urging said one face of said second hinge component towards said one face of said first hinge component.   
     
     
       3. A hinge joint as claimed in claim 2, with additionally: means for rotating said spindle between a first position and a second position,   said spindle being rotated into said first hub in said first position to cause said shoulder of said bushing to move away from said one end of said second hub,   said spindle being rotated out of said first hub in said second position to cause said shoulder of said bushing to bear on said one end of said second hub,   whereby, said one face of said second hinge component is urged toward said one face of said first hinge component by said spring in said first position of said spindle and said one face of said second hinge component is clamped against said one face of said first hinge component in said second position of said spindle.   
     
     
       4. A hinge joint as claimed in claim 3, wherein said means for rotating said spindle comprises: a crank fixed to the end of said spindle at said threaded end of said spindle,   and with additionally:   means for locking said crank against rotation.   
     
     
       5. A hinge joint as claimed in claim 4, wherein said crank comprises: a crank arm having one end thereof fixed to said end of said spindle at said threaded end thereof; and   a crank handle pivotally attached to end of said crank arm opposite said end of said crank arm fixed to said spindle,   said crank handle being movable between a first position in which said handle extends substantially perpendicular to said crank arm and a second position in which said handle lies substantially parallel to said crank arm.   
     
     
       6. A hinge joint as claimed in claim 5, wherein: said first hub of extends outward from the surface of said disk of said first hinge component opposite said one face thereof,   and wherein said means for locking said crank against rotation comprises:   a plurality of spaced apart striations extending longitudinally along the exterior surface of said first hub, and   a tang on the end of said crank handle opposite the end thereof attached to said crank arm,   said tang engaging one of said striations of said first hub when said handle is placed in said second position thereof.